<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <script type="text/javascript">
        	fn(1,2)
        	function fn(a,b){
        		//console.log(a+b);
        		//fn 为形式参数
        		//arguments为实际参数
        		if( fn.length == arguments.length){
        			alert(a+b);
        		}else{
        			alert("你输入的参数不对应该为"+fn.length)
        		}
        	}
        </script>
    </head>
    <body>
    </body>
</html>